In apparatus of this type, the shelves are superposed in two columns, disposed in front and to the rear, the first column masking the second.
The shelves are fixed to the mechanism at each of their lateral sides. There are therefore two identical mechanisms, connected by a motor shaft which passes through the apparatus.
On the other hand, the shelves are maintained horizontal by a lever bearing a roller engaged in a slideway, for each of the mechanisms. There are thus two slideways face to face.